1. Field of the Invention
The present invention relates to a lens-fitted photo film unit having an IC (integrated circuit). More particularly, the present invention relates to a lens-fitted photo film unit in which information of various kinds is written to a memory IC incorporated therein.
2. Description Related to the Prior Art
A lens-fitted photo film unit is pre-loaded with unexposed photo film, and includes a mechanism disposed in a photo film housing for taking an exposures. A flash built-in type of lens-fitted photo film unit includes a flash device constituted by a flash discharge tube, a flash circuit or charger circuit, and a dry battery. This type is convenient for use in taking exposures with flash light, mainly for scenes at night, indoors, or in the dark.
There are systems suggested in U.S. Pat. No. 4,443,077 (corresponding to JP-A 56-154720) and JP-A 2-217829 in which a memory IC or semiconductor memory is incorporated in a photo film cassette or cartridge, and in which exposure-taking information obtained by a camera upon an exposure is written to the memory IC to be used in a photo laboratory or by users.
Examples of exposure-taking information are exposure data, print format data, date data and caption data. The exposure data represents information of a shutter speed, an aperture stop, and existence of emission of flash light. The print format data represents any of printing aspect ratios of a standard size, a panoramic size and an L-size. If the camera has a structure suggested by JP-A 54-26721 for designating a trimming range, the print format data may represents the trimming range. The date data represents a date of taking an exposure. The caption data represents a sequence of letters input by a user of the camera with its pushbuttons or the like for recording a caption or phrase.
The exposure-taking information is read in the course of printing operation in a photo laboratory. For example the exposure data is used in control of exposure in the printing operation. The print format data is used for automatic determination of printing magnification, and a changeover of a negative photo film mask and a paper mask. It is possible to obtain photographic prints with an format or magnification desired by a user even if all exposures are taken at one equal frame format by the camera.
U.S. Ser. No. 08/784,259 (corresponding to JP-A 9-211680) suggests a lens-fitted photo film unit in which an memory IC is incorporated in its photo film housing or a photo film cassette pre-loaded therein. Exposure-taking information is written to the memory IC. A write control IC and the memory IC are supplied with power by a battery associated with a flash device. Upon the finish of taking each exposure, the write control IC writes the exposure-taking information to the memory IC.
If the flash circuit of the flash unit operates while the exposure-taking information is written, a comparatively great current flows in the flash circuit. The voltage of the battery drops in a temporary manner, to cause errors in operation of the write control IC or the memory IC. It is likely that no exposure-taking information is written to the memory IC, or that data different from the correct exposure-taking information is written.